TIMING SYNCHRONIZATION FOR THE UPLINK OF AN OFDMA SYSTEM

This paper deals with a new timing estimator for the uplink of an Orthogonal Frequency-Division Multiple Access (OFDMA) system. The estimator is based on the maximum likelihood (ML) criterion and exploits knowledge of two pilot symbols. Its main advantage is that it provides a feedforward estimate of the timing phase, thus allowing synchronization in only two OFDM blocks. In contrast to other existing schemes, it does not require that the subcarriers of a given user occupy adjacent positions in the signal bandwidth. This makes it possible to interleave subcarriers of different users so as to optimally exploit the frequency diversity of the channel.